By the wide use of computers and cell phones, computerization of the letter and pattern information by using such as personal computer communication, internet, and electronic mails has been rapidly advancing.
In such information communities, it is regarded as desirable to use complementarily voice synthesis, an electronic Braille display, and others as the means to obtain information for visually impaired persons. As the electronic Braille display, the so far used so-called six dot Braille is adopted. However, among visually impaired persons, only about ten percent can read such six dot Braille. This is because midlife blinds are increasing among aged people due, for example, to diabetes, and since it requires much effort for aged people to learn Braille, many of them give up learning on midway.
On the other hand, a tactile display is known as one of the means to communicate information for midlife visually impaired persons which can display letter shapes (ink letters) and pattern information as the moving of respective pins, that is, information of convex and concave positions by arranging actively moving pins vertically on a two-dimensional plane. As the drive means of pins in said electronic Braille displays or tactile displays, for example, such drive means as electromagnetic, electrostatic, piezoelectric actuators are adopted, and they are made up by moving respective pins to convex or concave positions by these drive means. The one using an electromagnetic actuator, for example, as a drive means is disclosed in the Japanese Patent laid open application JP 2002-207418 A (Reference 1) and the one using a piezoelectric actuator as a drive means is disclosed in the Japanese Patent laid open application JP H6-301335 A (1994) (Reference 2).
However, in Reference 1, since pins are driven by electromagnetic force generated by a coil, the coil has to be small-sized if the whole of it is to be small, and hence the electromagnetic force is weak. If thin wire is used for a coil, an electrical resistance of the coil is high, and the power consumption increases. In case of Reference 2, there is such a problem that, in order to displace a pin by 1 mm or more by, for example, a planar piezoelectric bimorph device as a drive means, the piezoelectric bimorph device itself becomes large, and the tactile display itself becomes large-sized, as well as drive voltage is relatively high.
On the other hand, a Braille pin driving device which reduced driving power and simplified the structure is disclosed in the Japanese Patent laid open application JP 2001-265213 A (Reference 3). This Braille pin driving device utilizes coils made of shape memory alloys, displacing pins by, for example, extension motion upon turning on electricity, and fixing and holding a stopper attached to the pin at two displacing position, that is, at a convex and a concave positions, by contacting to the fixed and arranged magnetic plate for magnetically fixing.
However, the three dimensional assembly structure of the Braille pin driving device of Reference 3 is complex, and it would be difficult to decide pin positions upon assembly.
Here, as the pin driving system in the above-mentioned References 1-3, pins are arranged at intervals of about 2.5 mm pitch, for example, close to the Braille specification, as well as driven by a drive means between convex and concave positions, and fixed and held at convex and concave positions. Therefore, though it is possible to express the above-mentioned six dots Braille, narrower pitches are preferable for finer expression in case, for example, pattern expression is performed with a number of pins arranged as a dot matrix. If also respective pins are fixed and held at a plurality of positions with regard to their axis direction, multi-value display and so-called gradation expression are possible.
However, as the pin drive system in the above-mentioned References 1-3, respective pins are not so designed to be arranged at narrow pitches, or fixed and held at a plurality of positions with regard to their axis direction. Also, in case of pattern display with a number of pins, and respective pins are driven by a driving device with the electromagnetic actuator, there is such a problem that the display speed is slow, as well as the motion noise is relatively loud.